This invention relates to devices for acquiring cell samples, particularly for medical or laboratory analysis. It is primarily directed to a biopsy device for obtaining tissue and cell samples for analysis but devices according to the invention are also useful for obtaining fluid samples, in particular blood. The device may be used in either human or veterinary medicine or in post-mortem examination.
In the diagnosis of human disease it is often necessary for the clinician, physician, or surgeon to obtain a sample of tissue or cells from the patient for examination by medically qualified tissue or cell analysts (histo or cytopathologists). Such samples may be obtained by open surgical biopsy, or by endoscopic biopsy, using specially designed forceps. Both these procedures are traumatic and expensive. Alternatively cell samples of the relevant tissue may be obtained by inserting a hollow needle (e.g. a standard blood sampling needle) into a lesion, and moving the cutting point backwards and forwards several times. The cells thus dislodged are taken up into the needle either by force of capillary attraction, or by the additional use of suction provided by a syringe, e.g. a standard 10 or 20 ml syringe. Using the needle alone, the sample obtained may be very small, or even inadequate. Tissue or cell material may be lost or wasted. Using the syringe increases the yield in most instances, but it is a difficult manoeuvre for untrained clinicians, or clinicians who do not perform the procedure on a regular basis. To overcome this latter difficulty, a pistol-type syringe holder known as a Swedish gun was developed which would allow the application of suction, and simultaneous passage of the needle, through the tissue using one hand only. For most people this instrument proves extremely awkward, inaccurate and traumatic. In addition the use of this physically large and intimidating device causes severe distress to patients in many instances.
It is well known in the field of phlebotomy (blood-sampling) to use an evacuated container for receiving blood samples. A hollow needle having front and rear pointed ends is mounted in a plastic needle holder. The front end of the needle is inserted into a vein and the rear end of the needle pierces a stopper or diaphragm on an evacuated tube which is slidable inside the needle holder. Blood is then sucked through the needle into the container. It is not generally necessary to interrupt the flow of blood until the required sample has been taken or the container is full. The container is then removed (while the front end of the needle may be retained in the vein) and a second evacuated container may be brought into use.
U.S. Pat. No. 4,697,600 suggests the use of an evacuated container in needle aspiration biopsy. It describes a method for obtaining tissue and cells by inserting one end of a fine hollow needle into an area of body tissue and inserting the other end into an evacuated container with pre-established vacuum. This is followed by continuously suctioning tissue and cell samples through the needle into the container. However with this device, after the rear end of the needle has pierced the stopper or diaphragm on the evacuated container, it is not possible to control the application of the vacuum precisely to the area to be sampled. The needle must be inserted into the body tissue before the evacuated container can be pushed into the holder, which involves a potentially distressing movement. Furthermore, once the hollow needle is removed from the body tissue the vacuum is lost. It is therefore necessary to use a second evacuated container, post removal from the tissue sample, to ensure that all tissue and cell samples are collected from the needle and into the container. Furthermore it is not possible to use the vacuum to suck preserving solution into the container after aspiration of the samples.
Known phlebotomy devices, and also the device of U.S. Pat. No. 4,697,600 suffer from the problem that the front end of the needle must be inserted into the vein or body tissue before the evacuated tube is pushed forward inside the needle holder. If the rear end of the needle pierces the stopper or diaphragm of the evacuated tube prematurely, the vacuum will be lost. It is however difficult to push the evacuated tube forward without a risk of traumatizing the vein or tissue in which the front end of the needle has been inserted.
Various proposals have been made for valve mechanisms in phlebotomy equipment e.g. WO 95/16395 and WO 95/28881. However these valves are intended to close the cannula to fluid flow except when an evacuated tube is in place and connected to the rear end of the cannula. U.S. Pat. No. 3,848,579 describes a blood-drawing device which has separate front and rear cannulas with an elasto-valvular mechanism between them. Various forms of valve are described, all of which are automatically activatable by application of the vacuum to the rear cannula. The valve mechanism prevents the occurrence of blood drips from the venous side into the ambient environment prior to the installation of the initial evacuated tube and/or during the span of time required to change from one blood-filled tube to a fresh evacuated tube, as occurs during the process of multi-sampling involving a single venipuncture. However the valve mechanism cannot be operated while the vacuum is applied to the cannula conduit.
U.S. Pat. No. 3,906,930 describes a blood-taking device having two valves. The first valve closes the rear end of the needle when a container is not connected to it and the second valve makes it possible to control the difference of pressure utilized for drawing blood. The second valve can be closed rapidly in the event it is discovered that the needle lies in tissue exterior to a blood vessel rather than in a blood vessel itself. The device is a relatively complex structure made in two joinable portions. The first valve is operated by joining and separating the two portions. The second valve is operated by rotating the container relative to the device. The problem with this device is that it would require 2 hands for operation and would be clumsy to use, with a risk of distress to the patient.
EP 033 528 describes a blood sampling device having a flexible tube linking two opposing needles. A variety of different valve means are provided, including using the user""s fingers to pinch the tube, the application of a roller valve and the provision of a cap. In all the described embodiments the flexible tube is in a normally open state and the valve is actuated to seal the tube. Such an arrangement is unsuitable for multiple passing tissue sampling.
WO 88/10286 describes disadvantages associated with blood sampling devices having normally closed valves, specifically the issue of sterilization of the valve and possible failure of the device due to wear and tear resulting from continual strain on the valve. WO 88/05286 addresses these problems by providing a cover for the device, the cover adapted to maintain the normally closed valve in an open position.
It is an object of the present invention to provide devices which can be used by clinicians to obtain cell samples with minimal distress to the patient or animal and in particular, in the case of a biopsy device to improve the chances of successfully recovering adequate tissue or cellular material for a testing while subjecting the cells and tissues to minimal shear and other stresses.
Accordingly the present invention provides a device and method for obtaining tissue or cellular samples as described in the appended claims.
The present invention provides a device for acquiring tissue or cell samples by aspiration into an evacuated container, the device comprising:
(a) a front hollow needle portion to be inserted into the body from which a sample is to be taken,
(b) a rear hollow needle portion for communicating with the evacuated container,
(c) a conduit connecting the front needle portion to the rear needle portion,
(d) a valve mechanism to open and close the conduit, characterized in that the valve mechanism is manually operable by one hand and controls the application of negative pressure in the front needle portion.
In a preferred embodiment, the conduit comprises a flexible tube and the valve mechanism comprises releasable means to pinch the flexible tube in a pressure-tight manner. The flexible tube may suitably be of silicone or other elastomeric plastics material which is acceptable in the medical/veterinary field. The term xe2x80x9cpressure tightxe2x80x9d and/or xe2x80x9cair-tightxe2x80x9d as used herein refers to a degree of tightness which is sufficient to inhibit a significant passage of air under the negative pressure applied by the type of evacuated container which is to be used.
More preferably, the valve mechanism comprises a spring-biased push-button operable by one digit of a user""s hand.
Suitably, the front and rear needle portions and the conduit are mounted longitudinally in a housing, and the valve mechanism comprises a slide member which is moveable transversely of the housing between a rest position and an activated position. Preferably the front and rear needle portions and the conduit are in alignment.
Preferably, the conduit comprising a flexible tube passes through an aperture in the slide member and is pinched against a fixed element of the valve mechanism when the slide member is in the rest position and is released to open the conduit when the slide member is in the activated position.
In the preferred embodiment the housing is manufactured from a translucent or transparent material.
In one embodiment which allows for ease of assembly of the device, one part of the conduit and the rear needle portion are formed from an elongate rigid tube provided with a break point at which the tube is breakable into front and rear parts, and a second part of the conduit is formed by flexible sheathing on the rigid tube.
In one embodiment the device may be used in the practice of tissue sampling. In another embodiment the device may be used in the practice of phlebotomy.
In further embodiments the device may be used in the practice of veterinary sampling, or for acquisition of samples in post-mortem examination.
The invention also relates to a method of acquiring body samples by aspiration into an evacuated container, utilizing a device comprising:
(a) a front hollow needle portion to be inserted into the body from which a sample is to be taken,
(b) a rear hollow needle portion for communicating with the evacuated container,
(c) a conduit connecting the front needle portion to the rear needle portion,
(d) a valve mechanism to open and close the conduit the valve mechanism being manually operable by one hand and controlling the application of negative pressure in the front needle portion, the method comprising the steps of:
(i) establishing communication between a pre-evacuated container and the rear hollow needle portion;
(ii) inserting the front needle portion into the body from which the sample is to be taken at the appropriate location for obtaining the desired sample;
(iii) actuating the valve mechanism for sufficient time, and repeatedly if desired, to apply negative pressure in the front needle portion so as to draw a sample through the front needle portion through the conduit to the rear needle portion and into the pre-evacuated container.
One embodiment of the invention will now be described by way of example, with reference to the accompanying drawings.